In offshore drilling environments it is necessary to supply hydraulic fluids to the wellhead and the standard practice up until relatively recently has been to use a standard thermoplastic hydraulic sub-sea control umbilical hose for the purpose of work over control where work over operations are performed on a sub-sea wellhead using a work over riser. These standard hydraulic sub-sea control umbilical hoses are placed outside the riser from the topside down to the wellhead.
Recent deepwater sub-sea exploration has created the demand and need to place the work over umbilical within the riser annulus of the drill string and conventional thermoplastic hoses have proved to be unsuitable for a number of reasons as follows:—                Temperature—Where a work over umbilical is inserted into the riser annulus the umbilical may be subjected to temperatures of up to 130° C. from the wellstream flowing through the riser core. High temperatures significantly reduce the mechanical properties of the polymers used in standard sub-sea control hoses causing end fittings to creep and fail. Additionally high temperatures affect the collapse resistance of the hose due to the reduction in the modulus of elasticity for the polymers used. Furthermore, at elevated temperatures polymers have a reduced resistance to chemical attack and for the rate of chemical attack to increase. Additionally at elevated temperatures the tensile strength of the pressure containment layer of a conventional braided hoses, typically an aramid fibre braided pressure containment layer, reduces and thus the burst pressure of the hose is reduced.        High external pressures—Deepwater sub-sea exploration now takes place in water depths of up to three thousand metres (3000 m) where differential pressures, that is the difference in pressure between the fluid in an umbilical and the surrounding riser annulus liquid (typically a mud having a specific gravity of 2 or more) can be up to 300 bar (30 MN/m2). High external pressures significantly reduce the tensile strength and fatigue resistance of the pressure containment layer, typically an aramid fibre braided pressure containment layer, as the material is sandwiched between a core tube and an outer jacket and is subjected to significant and damaging crush loads found at the wellhead in such deep water installations.        High working pressures—In order to operate the hydraulic control and chemical injection hoses at depths of up to 3000 m, where differential pressures are up to 300 bar (30 MN/m2), very high topside or ambient pressures are required, typically 1200 bar is required. Conventional standard thermoplastic hoses using aramid fibre braided layer technology to contain the working fluid at these elevated working pressures are unsuitable due to the limitations in material technology which give rise to reductions in the operational reliability of such hoses.        
Furthermore the muds used within the riser annulus create a highly corrosive, abrasive and volatile environment where conventional hose structures/hose materials are unsuitable.
It is an object of the present invention to avoid or minimise one or more of the foregoing disadvantages.